JPH09227764A - Epoxy resin composition for semiconductor sealing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an epoxy resin composition for sealing semiconductors having high mold releasability and reliability by adding a specific high-density polyethylene to an epoxy resin composition with improved productivity and reduced production costs. SOLUTION: This resin composition comprises (A) an epoxy resin (for example, o-cresol novolak type epoxy resin), (B) a phenolic resin curing agent (for example, a phenol-novolak resin, (C) a curing accelerator (for example, 1,8- diazabicyclo(5,4,0)undecene-7, (D) an inorganic filler (for example, spherical silica powder) and (E) fine particles of high-density polyethylene softening over 120 deg.C, having 80% and higher crystallinity and <=200μm average particle sizes as essential components.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is to obtain an epoxy resin composition for a semiconductor encapsulating resin having good moldability.

[0002]

2. Description of the Related Art Epoxy resin-based semiconductor encapsulating resin compositions have been developed and produced in order to protect IC bodies from mechanical and chemical effects. Items required for this change depending on the structure of the sealed IC package. Here 1
With the progress of surface mounting of IC packages in 0 years, a sealing resin composition having high solder crack resistance has been required.
In order to improve the solder crack resistance, the resin composition is forced to have a low water absorption. In order to reduce water absorption, it is necessary to improve the content rate of the inorganic filler, and for that purpose, low-viscosity epoxy resin and curing agent are required. However, since a low-viscosity epoxy resin or a curing agent has a slow curing reaction, a resin composition using the same generally has poor releasability. That is, there is a big problem that the molded product is not peeled from the mold, or that the mold is partially left on the mold at the time of mold release. It has been desired to develop a releasing agent that can release even a resin composition having poor curability.

[0003]

DISCLOSURE OF THE INVENTION The present invention provides a resin composition which improves the mold releasability of an epoxy resin composition for semiconductor encapsulation and is capable of satisfactorily molding / mold releasing even a resin composition having poor curability. Especially.

[0004]

Means for Solving the Problems The present inventor has made intensive studies to achieve the above object. As a result, it was found that the resin composition having the following composition was excellent in moldability and had no problem in reliability. That is, the present invention includes an epoxy resin, a phenol resin curing agent, a curing accelerator, an inorganic filler, and a softening point 1.
20 ° C or higher, crystallinity 80% or higher, average particle size 200μ
It is an epoxy resin composition for semiconductor encapsulation, which contains finely divided high-density polyethylene of m or less as an essential component.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Each composition will be described below. The epoxy resin used in the present invention refers to a compound having an epoxy group in the molecule. Examples thereof include orthocresol novolac type epoxy resin, bisphenol A type epoxy resin, bisphenol F type epoxy resin, triphenol methane type epoxy resin, naphthalene type epoxy resin, biphenyl type epoxy resin and the like. Also,
The degree of polymerization and epoxy equivalent of these resins are not particularly limited. However, in the case of surface mountable resin composition,
It is necessary to increase the amount of the inorganic filler, and an epoxy resin having a viscosity when melted as low as possible is desired. In order to improve the moisture resistance reliability, it is desirable that chlorine ions, sodium ions and other free ions contained in these epoxy resins be as small as possible.

The phenol resin curing agent used in the present invention refers to a compound having a phenolic hydroxyl group in the molecule. Examples thereof include phenol novolac resin, paraxylylene-modified phenol resin, triphenol methane type phenol resin, and bisphenol A. There is no problem if these curing agents are modified with silicone. Further, the hydroxyl equivalent, the degree of polymerization, etc. are not particularly limited. Similar to the epoxy resin, a curing agent having a relatively low viscosity tends to be desirable for the surface mounting sealing resin composition.
Further, in order to improve the moisture resistance reliability of these resins, it is desirable that chlorine ions, sodium ions and other free ions contained as impurities are as small as possible.

The curing accelerator used in the present invention may be any one that accelerates the chemical reaction between the epoxy group and the phenolic hydroxyl group. For example, 1,8-diazabicyclo (5,
4,0) undecene-7 (DBU), 2-methylimidazole, triphenylphosphine, tetraphenylphosphine / tetraphenylborate and the like can be mentioned. In the case of a formulation containing a low-viscosity epoxy resin and a curing agent, if the reactivity of the curing accelerator is not high, the hardness after molding will be low, and mold release will occur, so the curing reaction may proceed sufficiently under the molding conditions. It is more desirable to select the type and amount of the curing accelerator that can be used.

The inorganic filler used in the present invention includes:
Fused silica powder, spherical silica powder, crystalline silica powder, 2
Examples of the secondary agglomerated silica powder, alumina, and the like are preferable, and spherical silica powder is preferable from the viewpoint of improving the fluidity of the resin composition. Regarding the shape of the spherical silica powder, in order to improve the fluidity, it is desirable that the shape of the particles themselves be infinitely spherical and that the particle size distribution be broad.
The inorganic filler may be surface-treated in advance with a silane-based, titanium-based or other surface-treating agent. The compounding amount of the inorganic filler is not particularly limited. Further, the average particle diameter and the maximum particle diameter are not particularly limited.

The high-density polyethylene used in the present invention is an important technical point in the present invention, and therefore will be described in detail. Since polyethylene has a low surface energy, it is easy to bleed out on the surface of the molded product during molding even if it is kneaded into various compounds (not limited to the resin composition for semiconductor encapsulation). It has been used as an agent.

By using the high-density polyethylene of the present invention, the following points are improved in the characteristics of the epoxy resin composition. Since the surface energy of high-density polyethylene is low, good releasability can be exhibited with a small amount of addition.
Since this high-density polyethylene has a high softening point and a high viscosity during molding, there is little mold fouling during continuous molding. Further, it has excellent long-term thermal stability, and the number of times of cleaning the mold is reduced. Since the surface energy of high-density polyethylene is low, it adheres well to various metals of lead frames and various plastics, and the adhesive strength and moisture resistance are improved.

The features and usage will be described in detail below. The softening point of the high density polyethylene used in the present invention is 120 ° C. or higher. Since the resin composition for semiconductor encapsulation is usually kneaded at about 100 ° C., the softening point is 12
It was thought that uniform dispersion at the time of kneading was impossible when the temperature was higher than 0 ° C, but experiments revealed that kneading could be performed without problems. Although the reason is not clear, it is presumed that the high shearing force at the time of kneading causes the epoxy resin and the curing agent to mix due to the solvent effect, resulting in uniform dispersion. From the results of some experiments, it was found that the high-density polyethylene having the above-mentioned softening point is effective in improving the releasability.

The softening point of the high density polyethylene in the present invention is preferably 120 ° C. or higher. High-density polyethylene having a softening point of less than 120 ° C. tends to cause a problem of mold fouling in continuous molding. The method of measuring the softening point in the present invention is the ring and ball method, which has an inner diameter of 15.9 mm and a depth of 6.4.
Melt the test piece into a brass ring of mm and cast it, or fit the molded or punched one, put a steel ball with a diameter of 9.53 mm and a weight of 3.5 g on the center, put it in an oil bath, The liquid temperature is raised at 5 ° C / min. As the temperature rises, the steel balls fall. The softening point is the temperature of the oil bath when the steel ball comes into contact with the plate 25.4 mm below the lower end of the brass ring.

The high-density polyethylene used in the present invention is a high-density polyethylene having a crystallinity of 80% or more. If the degree of crystallinity is less than 80%, the crystallinity is low, so that it is likely to cause oxidative deterioration due to heat, and in continuous molding at high temperature for a long time, the oxidized polyethylene sticks thickly to the mold surface It is the main cause of dirt. The crystallinity is measured by the density method, in which polyethylene fragments are placed in a test tube in a water bath at 25 ° C. and a mixture of water and ethanol is added. Change the blending ratio of water / ethanol to make the polyethylene fragments float. The specific gravity of the water / ethanol solution in this state is measured with a pycnometer to calculate the specific gravity of polyethylene. Since the specific gravity of polyethylene is known for both amorphous and crystalline substances, the crystallinity is calculated based on the data based on the following formula. Crystallinity (%) = ρ _c (ρ−ρ ₂ ) / ρ (ρ _c −ρ ₂ ) × 1
Where ρ is the specific gravity of polyethylene, ρ _{c is} the specific gravity of the crystals of polyethylene, and ρ _{2 is} the non-crystalline specific gravity of polyethylene.

Further, it is necessary that the average grain size is made finer to 200 μm or less. Since the softening point is 100 ° C. or higher, which is the kneading temperature, it is basically difficult to knead. Therefore, it must be pulverized in advance before kneading. From the experimental results, it was found that the average particle size is preferably 200 μm or less. When the average particle size exceeds 200 μm, polyethylene is not uniformly dispersed, which causes mold fouling. The method for measuring the average particle size in the present invention was analyzed using a laser particle size analyzer manufactured by Horiba Ltd. The dispersion medium is a water / ethanol mixture.

The molecular weight and molecular weight distribution of the high-density polyethylene used in the present invention, and the primary structure of the polymer such as branched or linear are not particularly limited. The softening point, crystallinity, and average particle size are the most important parameters. The compounding amount of the high-density polyethylene in the present invention is 0.02 to the total sealing resin composition.
1.00% by weight is desirable. If it is less than 0.02% by weight, it does not sufficiently function as a release agent, resulting in defective release.
If it exceeds 1.00% by weight, the high-density polyethylene will bleed out to cause problems such as mold fouling, burrs, and poor adhesion to the lead frame.

The high-density polyethylene of the present invention may be used in combination with other types of release agents or may be used alone without any problem. However, the other release agent when used in combination is 2 out of all the release agents.
Less than 0% by weight is desirable. If it exceeds 20% by weight, any of the mold stains, mold releasability, and adhesion to various base materials is deteriorated, and the balance of properties as a resin composition is lost. The release agent used in combination is preferably an ester wax such as carnauba wax or an acid wax such as stearic acid wax or lead stearate, but is not particularly limited. In addition to the above-mentioned components, the resin composition of the present invention may optionally contain a coloring agent such as carbon black, a brominated epoxy resin, a flame retardant such as antimony trioxide, a silane coupling agent, a silicone oil, and a rubber. A stress component can be added. The resin composition of the present invention is an epoxy resin, a phenol resin curing agent, a curing accelerator, an inorganic filler, and other additives are mixed at room temperature with a mixer, kneaded with a general kneader such as a roll and an extruder, and cooled. It can be pulverized afterwards to obtain a molding material.

[0017]

EXAMPLES The present invention will be specifically described below with reference to examples.
<< Example 1 >> The following composition Biphenyl type epoxy resin (epoxy equivalent: 195) 5.8 parts by weight Phenol aralkyl type resin (hydroxyl equivalent: 175) 5.7 parts by weight Spherical silica powder 85.0 parts by weight High density polyethylene A 0.5 parts by weight 1.8-diazabicyclo (5,4,0) undecene-7 0.2 parts by weight carbon black (average particle size 18 nm) 0.3 parts by weight Brominated phenol novolac type epoxy resin 1.0 parts by weight 1.3 parts by weight of antimony trioxide and 0.5 parts by weight of an epoxysilane coupling agent were mixed at room temperature with a mixer, kneaded with a biaxial roll at 100 ° C., cooled and pulverized to obtain a molding material. The obtained molding material was evaluated by the following evaluation methods.

<< Evaluation Method >> Softening point: Ring and ball method Crystallinity: Density method Molding evaluation: 160 pQ of low pressure transfer molding die
An FP molding test was performed. The mold releasability of a molded product molded at a molding temperature of 175 ° C. and a curing time of 2 minutes is sensory-evaluated in three grades of ◯, Δ, and x. Further, the state of the surface of the obtained molded article was visually observed, and the presence or absence of mold contamination was determined in three stages of ○, Δ, and ×. Solder resistance evaluation: 80 pQFP (1.
A molded product (5 mm thick) was obtained and post-cured at 175 ° C. for 8 hours to obtain a sample. Six packages were obtained for each part number. After being placed in a constant temperature and humidity chamber at 85 ° C. and 85% for 168 hours, an IR reflow treatment at 240 ° C. was performed. The peeling inside the package after the treatment was observed with an ultrasonic flaw detector, and the solder resistance (and adhesion) was determined based on the number of packages having the chip surface peeling and the pad back surface peeling.

<Examples 2 to 6> Formulated according to the formulation of Example 1 in which only the type of high-density polyethylene was changed as shown in Table 1 as the release agent (other formulations are the same as in Example 1). Then, a molding material was obtained in the same manner as in Example 1 and evaluated in the same manner. However, in Example 6, carnauba wax was used in combination. << Comparative Examples 1 to 5 >> Among the formulations of Example 1, formulations in which the type of high-density polyethylene as the release agent or the compounding amount of the release agent and spherical silica were changed as shown in Table 2 (other formulations are those of Example 1).
The same) as above, and a molding material was obtained in the same manner as in Example 1 and evaluated in the same manner.

* Characteristics of high density polyethylene used Softening point Crystallinity Average particle size (° C) (%) (μm) High density polyethylene A 142 96 105 High density polyethylene B 125 95 105 High density polyethylene C 140 85 105 105 High Density Polyethylene D 143 97 195 High Density Polyethylene E 162 98 53 High Density Polyethylene F 111 81 103 High Density Polyethylene G 124 79 102 High Density Polyethylene H 142 96 96 266

Table 1 Example 1 2 3 4 5 6 compounding (parts by weight) Biphenyl type epoxy resin 5.8 5.8 5.8 5.8 5.8 5.8 Phenol aralkyl type resin 5.7 5.7 5.7 5.7 5.7 5.7 Spherical silica 85.0 85.0 85.0 85.0 85.0 85.0 High density polyethylene A 0.5 0.2 High-density polyethylene B 0.5 High-density polyethylene C 0.5 High-density polyethylene D 0.5 High-density polyethylene E 0.5 Carnauba wax 0.3 Characteristic releasability ○ ○ ○ ○ ○ ○ Mold contamination ○ ○ ○ ○ ○ ○ Solder resistance evaluation: Chip peeling 0 0 0 0 0 0 Solder resistance evaluation: Pad peeling 0 0 0 0 0 0 0

Table 2 Comparative Example 1 2 3 4 5 6 7 Compounding (parts by weight) Biphenyl type epoxy resin 5.8 5.8 5.8 5.8 5.8 5.8 5.8 Phenol aralkyl type resin 5.7 5.7 5.7 5.7 5.7 5.7 5.7 Spherical silica 85.0 85.49 84.3 85.0 85.0 85.0 85.0 High density Polyethylene A 0.01 1.2 0.05 High density polyethylene F 0.5 High density polyethylene G 0.5 High density polyethylene H 0.5 Carnauba wax 0.5 0.45 Characteristics Releasability △ × ○ △ ○ ○ ○ Mold stain resistance △ ○ × △ × × × Solder resistance evaluation: Chip Peeling 1 0 2 1 1 2 1 Solder resistance evaluation: Pad peeling 2 0 3 2 1 1 0

[0023]

EFFECTS OF THE INVENTION According to the present invention, a highly reliable epoxy resin composition for semiconductor encapsulation having good releasability can be obtained, so that the productivity of the semiconductor manufacturer is improved and the production cost of the semiconductor manufacturer is reduced. It can be reduced.

Claims (1)

[Claims] An epoxy resin, a phenol resin curing agent,
An epoxy resin composition for semiconductor encapsulation, which comprises a curing accelerator, an inorganic filler, a softening point of 120 ° C. or higher, a crystallinity of 80% or higher, and a micronized high-density polyethylene having an average particle diameter of 200 μm or less as essential components.